1. Field of the Invention
The present invention relates to an endoscope with a light guide composed of a bundle of optical fibers and a method for manufacturing the light guide.
2. Description of the related art including
information disclosed under .sctn.1.97-1.99:
In conventional endoscopes, an illumination light is supplied to the distal end of an insertion section through a bundle of optical fibers. The fiber bundle includes a number of elongate glass fibers o optical fibers. These fibers are bundled and contained inside the insertion section. The distal end portion of the optical fiber bundle is solidified by means of a bonding agent or the like, and is fitted with a mouthpiece thereon. The mouthpiece is attached to the distal end portion of the insertion section of the endoscope. The distal end portion of the fiber bundle is solidified as follows. First, those parts of the glass fibers at the distal end portion ar bundle closely and inserted into a die. Then, the bonding agent is poured into the die. At the proximal end portion of the optical fiber bundle, on the other hand, the individual glass fibers are kept free, without being bundled, in order to maintain flexibility.
If the proximal end portion of the optical fiber bundle, as well as the distal end portion, is joined close to one another when it is contained in the insertion section, its free action is restrained. As a result, the fiber bundle, and therefore, the insertion section of the endoscope, lose their flexibility.
Thereupon, in a typical endoscope, such as the one disclosed in Japanese Patent Disclosure No. 58-190912, the side wall of a cylindrical mouthpiece, used to retain the distal end portion of an optical fiber bundle, is thickened. Also, a sufficient space is secured between the outer peripheral surface of the fiber bundle and the inner peripheral surface of a holding portion of an insertion section of the endoscope. Thus, the density of glass fibers is lowered at the proximal end portion of the fiber bundle.
In such a typical endoscope, the side wall of the mouthpiece at the distal end portion of the insertion section is thick, as described above, so that the insertion section must have a large outside diameter. Thus, the insertion section is too bulky and heavy.